Object.factory

[Sean Kelly]

Max Samukha wrote:
> On Wed, 26 Sep 2007 16:40:21 +1000, Daniel Keep
> <daniel.keep.lists at gmail.com> wrote:
> 
>>
>> DanO wrote:
>>> Sean Kelly Wrote:
>>>
>>>> DanO wrote:
>>>>> I have found that this works quite well for non-templated classes, but templated classes don't seem to behave.  I am using the ClassInfo's name property to get the string, and that doesn't work.
>>>>>
>>>>> <code>
>>>>> class TDict(T)
>>>>> {
>>>>>     T[char[]] dict;
>>>>> }
>>>>>
>>>>> char[] tInfoName = TDict!(int).classinfo.name; // returns TDict!(int).TDict
>>>>>
>>>>> Object o = Object.factory(tInfoName);   // returns null
>>>>> </code>
>>>>>
>>>>> I have not tried 'Object.factory("TDict!(int)")'; it may work just fine.
>>>>>
>>>>> Anyone have any idea if this is supposed to work or is supported?
>>>> Try calling:
>>>>
>>>>      TDict!(int).classinfo.create();
>>>>
>>>> Instead.  ClassInfo also has a static find(char[]) method to perform 
>>>> lookups without going through Object.  Personally, I've never seen a 
>>>> reason to have the Obejct.factory() method, given what's in ClassInfo.
>>>>
>>>>
>>>> Sean
>>> Your solution doesn't help, since I really need to be able to use the class name to instantiate the object.  I am doing serialization and I don't know the object's class.  I have tried the ClassInfo.find(str).create() approach, and the doesn't work either.  I'm sure Object and ClassInfo are using the same database.
>>>
>>> Whatever the problem, I was just trying to remove the need to register my own factory function for those types, but unless someone replies with some more help, I will just use my tried and true method.
>>>
>>> -DanO
>> This seems to be a limitation with templated classes, so have you tried
>> non-templated?
>>
>> class TDict!(T) { ... }
>>
>> class IntDict : TDict!(int) { mixin TDict!(int).ctors; }
>>
>> auto instance = Object.factory("IntDict");
>>
>> This might be a pain in the arse, but it might work.  The other thing to
>> remember is that TDict *does not* generate any code.  Only specific
>> instances do.  So even if you could instantiate a templated class via
>> Object.factory, you'd still likely need to manually specify a finite
>> list of classes that should be instantiated.
>>
>> 	-- Daniel
> 
> It seems like a compiler bug. Classes from instantiated templates do
> not get added to localClasses array of ModuleInfo. What is the reason
> for that?

If I had to guess, I'd say it's because templates can be instantiated 
anywhere, but their 'home' is the module in which they are defined.


Sean